About Square Footage Calculator
Who we are, how our calculators are tested, and how to reach us.
Who we are
One job: measuring floor space correctly
Square Footage Calculator is a small, independent site. Homeowners use it to plan flooring and renovations, buyers and sellers use it to check a home’s living area, and contractors use it to price jobs by the square foot.
Every calculator is free, works on any phone or computer, and takes measurements the way you take them: feet and inches, yards or metric.
- 4Free calculators
- 0Measurements stored
- Z765ANSI rules for homes
- 6Units, ft + in to cm
Our method
How we build and test our calculators
Standard formulas only
Rooms use length × width, with the textbook formulas for L-shapes, circles, triangles and trapezoids shown on each page.
Exact unit definitions
1 foot = 0.3048 m, 1 sq ft = 144 sq in, 1 sq yd = 9 sq ft and 1 acre = 43,560 sq ft.
Appraisal rules for homes
The house calculator follows the ANSI Z765 approach Fannie Mae requires: above-grade area is reported apart from basements, and spaces under 7 ft are not living area.
Tested, and private
Every calculation is checked against worked examples (12 ft 6 in × 10 ft 3 in = 128.13 sq ft) before release. Calculations run in your browser; we never send or store what you type.
Results are for planning. For a sale, appraisal or construction contract, confirm measurements with a licensed appraiser or contractor.
Editorial standards
Sources, reviews and corrections
Primary sources
Measurement rules come from the ANSI Z765 standard and Fannie Mae’s Selling Guide. Unit definitions follow NIST. Flooring coverage and waste ranges come from manufacturer installation guides.
Reviewed and dated
Each calculator page shows the date it was last tested. We re-check formulas, examples and FAQs whenever a page changes, and at least twice a year.
Open corrections
If you find a wrong result or an unclear answer, email us with the numbers you entered. Confirmed fixes are published on the affected page with a new test date.
Independent and ad-free: we are not paid by flooring brands, retailers or real estate companies, and no calculator result is influenced by a sponsor.
Contact
Spotted an error, or have an idea for a feature? We read every message, usually reply within two business days, and fix confirmed errors quickly.